Commitments and Contingencies - Rent Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other commitments
Rent expense	$ 3,300	$ 3,100	$ 3,100
Lease liability assumed	10,997
Discontinued operations | UK Office Lease
Other commitments
Rent expense	500	500	500
Sublease income	$ 600	$ 100	$ 0